I don't know if they've had them done, but you can make boobs look huge by putting them in a pushup and putting the equivalent of a saline implant (a "cutlet" or two) into the bra under the breast. More or less the modern equivalent of tissue-stuffing your bra.
In the photo where Beyonce's boob looks weird, it could be that her cutlet shifted and was no longer severely pushing up the right side of her breast. It makes sense if you think about it.
I am really large-chested and wish I were small chested for a bunch of reasons. My boobs are heavy, they hurt and get in the way, buttonup shirts don't fit, they're uncomfortable in summer, and I *always* have to wear a bra. I think a lot of ladies want to get them enhanced for looks, but I would prefer mine were smaller for physical comfort.